Spark plug



. Aug, 23, 193s.` w. HARPER. JR 2,127,512

i SPARK PLUG Filed Julie 15, 1956 @i 'l fly/ I ...Il

' A?" fg ATTORNEY lPatented Aug. z3, 193s y UNITED ASTATES I'F.fri-:ivr oEFiCEY `signor to H. B. Motor. Corporation, New York, N. Y., a corporation of New York v Application Jima 13,`

17 Claims. This invention relates to spark plugs, and aims to increase the eiiiciency and smoothness of operf ation of internal combustion engines. The rapidity of the ignition of the fuel mixture contained in an internal combustion engine is one of the factors which affects the power output' per unit of fuel and also the smoothness ofoperation. For most satisfactory operation of the engine, the ignition of the entire fuel charge should be. as nearly as possible instantaneous.

I have ascertained that the rate of propagation fuel is small compared to the displacement volume of the piston, it is of substantial volume in 'comparison with the volume of fuel drawn in when the engine is throttled down. The presence of burnt gases mixed with the incoming i'uel appears to have the effect of reducing the speed of propagation of the iiame when the charge is ignited from a spark, as is customary. The slowness of the ignition materially reduces the eiciencyof the engine.

'I'he spark plug which I have invented produces practically instantaneous ignition, even when the fuel and air mixture in the engine is diluted with burnt gases.` Its use thus adds to thefuel einciency of automobile engines. It has also other ,advantages which will hereinafter appear from a detailed description of the spark plugs embodying my invention, which are shown as illustrative examples in the accompanying drawing in which:

Fig. lis anaxial section of a unitary-spark plug embodying the invention and adapted to be screwed into an opening ln a cylinder head;

Fig. 2 is a transverse section on the line 2-2 of cylinder;

Fig. 4 is an axial section of acomposite spark plug similar to that shown in Fig. l, except that it consists of an ordinary spark plug screwedinto special casing;

1936, Serial No. 845991 (Cl. 12R-169) Fig. 5 is a transverse sectiony on the line 5--5 of l Fig. 4;

Fig. 6 is an axial section of a unitary spark plug .adapted to be screwed into the wall of a cylinder;

and

Fig. 7 is a transverse section on the line 1 1. of Fig. 6.

The spark plug shown in Figs. 1, 2 and 3 includes an insulator I I of ordinary construction, a

metal body I2 ofspecial construction, and two electrodes I0, 2i. The insulator Il is preferably a porcelain insulator with a long skirt such as is used in the Champion .14 mm. spark plug. 'Ihe body I2, which most desirably consists of :a Isingle piece of metal, has a nut portion I5, an externally l threaded tubular portion I6 which extends well` beyond the inner end ofthe insulator II, and a shield portion I1 which substantially closes the ,inner end of the tubular portion but contains passages hereinafter described. In the. form illustrated in Fig. 1, the shield portion I'l provides a hollow projection of reduced diameter projecting from the inner end of the tubular portion I6. The body I2 supports the insulator II inthe usual manner, a nut I3 being used to secure the insulator to the body. 'I'he tubular portion I6 and the shield portion I'l, of thev body-enclose the inner end portion of the insulator II, and provide :a `chamber I4. The chamber I4 has a cylindrical portion I8 within the tubular portion I6 lof the body, a well I9 of reduced diameter within the shield I'l, and a aring portion 20 connecting the wellL and the cylindrical portion. The body I2 carries a transverse electrode 2I beyond the inner end of the insulator II. The electrode 2I cooperates with the central rod electrode I0 to provide a spark gap 22 at the inner end of the cylindricalV portion I8 of the chamber I4.

When the body I2 is screwed into the spark plug opening of a cylinder, the threaded portion I6 of the body is in the wall of the cylinder head, while the shield I1 of the body projects inwardly from the cylinder head into the lclearance space provided between the cylinder head and the end of the piston. The chamber It` is placed in communication with the cylinder by passages or bores 23 extending through the side Wall of the projecting shield I'l from its outside to the well I9. As seenjin Fig. 1, the bores 23 are inclined upwardlyifat a small angle as they enter the Well I9. As seenin Fig. 2, the bores 23 are inclined to radii the body so that they enter the well I9 tangentially.

The operation of this spark plug is as follows: During the compression stroke of the engine, the

fuel mixture, which may be diluted with a certain amountI of burnt gas, enters the chamber It through the bores 23, displacing burnt gas remaining in the chamber into the upper portion of the chamber surrounding the insulator I I, so that the fuel mixture lls the lower portion of the chamber ifi and surrounds the spark gap 22. IFrom the inclination of the bores, it results that the fuel mixture enters as a swirling body of gas rising from the well I9 into the lower part of the cylindrical portion I of the chamber Id. This swirling body of gas displaces the burnt gas in shield I1.

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the chamber without substantial'intermixture therewith. The spark gap 22 is located substantially on the axis of the swirling body of fuel mixture. This places the fuel mixture in the best condition for quick ignition from a spark in the gap, since the molecules of fuel in the swirling body are directly exposed to a spark at the gap, even though they are separated by molecules of burnt gas between them. Furthermore, as the bores 23 are not directed towards the spark gap and the spark gap is located axially in the swirling mixture, there is no current of gas across the spark gap which, by its blowing action, would interfere with the electiveness of the spark. It follows that when a spark is produced at the gap 22, the fuel mixture in the lower portion of the chamber I4 is instantly ignited. The expanding burning gas passes out through the bores 23 as jets of ame extending well into the body of mixture in the clearance space between the cylinder head and the'piston, so that this body is instantly ignited by direct contact with the ame, even though-the presence of molecules of burnt gas between the fuel molecules tends to reduce the rate of ame propagation in the mixture.

The insulator I I is protected from radiant heat from the burning mixture in the cylinder by the This result is attained by so directing the passages 23 that no straight line which can be drawn through them will intersect the insulator.

The spark plug shown in Figs. 1 and 2 is pro- ,vided with means for regulating and observing the width of the spark gap. 22.' 'I'he transverse electrode 2| has a drive fit in the body I2, so that the distance of its end from the rod electrode I may be varied by driving it in or out in this hole. In order that the adjustment may be observed after the spark plug has been assembled, a transverse bore 24 is provided'in the threaded 4portion I6 of the body. As seen in Fig. 2, this bore is not quite diametrical, but has its axis nearly on a. tangent to the rod electrode I0 so as to provide a small window through which th'e width of the spark gap 22 may be observed before the spark plug is screwed into the cylinderhead. After the spark plug has been screwed in, the ends of the bore 24 are closed by the wall of the cylinder, so that the presence of this bore does not interfere with the operation which has been described.

Figs. 4 and 5 show an ignition device similar to that shown in Fig. l, except that the one-piece body I2 is replaced by a composite body consisting of the body 25 of an ordinary spark plug 27 I and a special casing 25 Into which the'spark plug 26 is. screwed. The casing 25 hasA a nut portion I5' and a tubular'portion I6' which is threaded internally for reception of the spark plug body 26, and also threaded externally like the tubular portion of the ignition device shown in Fig. l.. The shield I1' at the end of the tubular portion I6 and the well and bores contained therein are similar to corresponding parts in Fig. l. The casing 25 carries no electrode, since a spark gap 22 near the lower end of the cylindrical portion i8 of the chamber It is provided by the two conventional electrodes I0', 2| of the spark plug 2. I

It is thus apparent that the casing 25 provides an attachment which may be screwed upon an ordinary spark plug to provide an ignition device similar to that shown in Fig. 1.

The spark plug shown in Figs. 6 and 7 is designed to be placed in an opening in a cylinder wall rather than in a cylinder head. The tubular portion |62 of its body |22 is closed at its end by a shield I'I2 having thel form of a transverse wall with concave inner and outer surfaces. At the center of the inner surface of this wall is an electrode 2|2 which cooperates with the central rod electrode |02 to provide a spark gap 222 near the lower .end of the chamber |452. Passages or bores 232 extend through the wall |12. The bores `232 are inclined outwardly from the axis of the device as they pass inwardly through the-shield |12. At the inner en'd of each bore is a deiiectingv surface 28 which directs gas entering through the bores toward the axis of the device above the spark gap 222. In this case, the body of fuel mixture entering through the bores tends to swirl ignited, is directed in the general direction of the Y axis of the device, so that the flame passes across the fuel mixture contained in the clearance space between' the cylinder head and the piston from a point on the circumference of this space.

The width of the spark gap 222 may be adjusted by placing shims between the insulator II2 and the shoulder of the body |22 on which the insulator rests. The adjustment may be observed through a diametrical window bore 242 in the tubular portion |62 of the body.

In this specification and in the claims which follow, the words inner end have been used in connection with various parts of the spark plugs to indicate the end which is directed into the cylinder when the spark plug is in use, that is to say, the lower ends of the parts of the spark plugs as they appear in Figs. 1, 4 and 6. l x

While the drawing shows three of the passages 23, the number of passages may be varied as del sired without departing from my invention, and it is practical, although less desirable, to use only one such passage. Consequently, in the claims which follow the number of passages is not specied and the word passages" where used in the f claims should be understood to include the use of metal body supporting the insulator and yforming arancia throng-hits side walls directed towards points spaced from the spark gap.

2. A spark I,plug -comprising an insulator, a

a casing providing an enclosed chamber surrounding the inner end of the insulator andfhav- A ing a cylindrical portion anda well oi reduced diameter, the casing containing restricted passages entering said well and inclined towards the I cylindrical portion of the chamber close toits inner end.

3. A spark plug comprising an insulator, a metal body supporting the insulator and forming a casing providing an enclosed chamber surrounding theinner end of the insulator and having a cylindrical portion and a well oi' reduced diameter, said casing containing a plurality of restricted passages entering the well of the chamber tangentially, and electrodes positioned to provide aspark gap located close to the inner end yoi the cylindricalportion of the chamber.

. 4. A spark plug comprising an insulator, a metal body supporting the insulator and forming a casing providing an enclosed chamber surroundingthe inner end of the insulator and having a cylindrical portion and a well of reduced diameter, said casing containing a plurality oi restricted passages, each having alength greater than' its width and entering the well of the chamber tangentially and inclined toward the inner end of the cylindrical portion of the chamber, and electrodes positioned to provide a spark gap located close to the inner end of the cylindrical portion of the chamber and near the axis o! the chamber so that it is not in line with said tangential passages.

- 5. The method of igniting a fuel mixture in an internal vcombustion engine, which consists in causing a small part of the mixture to swirl about an axis, producing a spark within the swirling body of gas at an intermediate point of its axis to ignite this part of the mixture, and projecting jets of flame produced 'by the ignition in this part oi'the mixture into the main body oi' the mixture. l

46. A spark plug comprising an insulator, a

' metal body supporting the insulator and forming a casing providing an enclosed chamlmr surrounding the inner end of the insulator, electrodes positioned to provide a spark gap near the inner end of thechamber, said casing containing a restricted passage so directed as to cause gas entering therethrough to swirl in the inner end portion of the chamber about the spark gap as Ia center and so proportioned that a straight line 4 drawn through it cannot intersect the insulator.

7. A spark plug comprising an insulator, a

- as to create a zone of reduced pressure therein,

producing a spark in this zone of reduced pressure to ignite this part of the mixture, and projecting 10. A spark plug comprising electrodes, an ln- I sulator, and a metal body supporting the insulator and the electrodes and forming a casing providing an enclosed chamber surrounding the inner end of the insulator and containing passages all'vof which enter the chamber tangentially at points spaced from its axis.

11. A spark plug comprising an insulator, a metal body supporting the insulator and forming a casing providing an enclosed chamber surrounding the inner end oi the insulator, and electrodes positioned to provide 'a spark gap in the chamber, said casing vcontaining restricted passages so inclined and arranged as to direct all gas entering the chamber against the outer circumferentiai wall of the chamber immediately upon its entrance and before it strikes the insulator or the spark gap.

12. A spark plug comprising an insulator, a metal body supporting the insulator and having an externally-threaded tubular portion extending beyond the inner end of the insulator, a shield closing the inner Aend of said tubular portion, and electrodes positioned to provide a spark gap near the inner end of-the chamber enclosed by the body and shield, said shield containing restricted passages, all of which are so inclined that the ams of no one of Athem intersects the insulator and the axis of no one of them passes through the spark gap.

13. A spark plug comprising an insulator, a

metal body supporting the insulator and forming '45 voi the insulator, and electrodes positioned to proan enclosed casing surrounding the inner end vide a spark gap in the chamber, said casing' containing a plurality of restricted passagm so insulator and a metal bodysupporting the insulator and forming a casing providing an enclosed chamber surrounding the inner end of the insulator, said casing containing restricted pmg'es so inclined and arranged as to direct all gas entering the chamber'against the outer circumferential wall oi the chamber immediately upon its entrance and before it strikes the insulator.

15. In a. spark plug, the combination of an insulator, a metal body supporting theinsulator and having an externally-threaded tubular portion extending beyond the inner end of the insu-` lator, and a shield closing the inner end of said tubular portion and containing restricted pas? 'sages havi line drawn through any one of them cannot intersect'the insulator. 16. A spark plug comprising electrodes prolviding a sparkgap, an insulator, and a metal body forming lssjcasing vproviding an. enclosed chamber surrounding thel inner endo! the insulengths at least oneshali as great as. their wi ths and all so inclined that a straight rounding the inner end of the insulator and containing passages inclined so as to cause the entering gas to swirl about the exis of the chambei', and a. pair of electrodes positioned to provide a. spark gap in the chamber spaced from its inner endand substantieily on its exis.

1 HARPER, Jal 

